The present invention is directed to a defoamer composition which does not contain any oils or short chain (C2-6) alcohols for use in groundwood and thermomechanical pulping operations.
The problem of foam in pulping operations is a continuing one, particularly in groundwood and thermomechanical pulping. Heretofore in these mechanical pulping processes (in contrast to chemical (sulfate) xe2x80x9cKraftxe2x80x9d pulping processes), the foam problem has been most effectively dealt with by using polyethylene glycol fatty acid esters which are generally dispersible in water. The esters have been made into stable microemulsions only by the use of undesirable mineral oils and/or short chain alcohols, e.g. iso-propyl or butyl alcohol. Typically, these microemulsions have an overall composition of about 30 to 60% by weight polyethylene glycol fatty acid ester, 5 to 20% oil, 5 to 20% alcohol, and 20 to 45% water. While an oil and/or alcohol are needed to manufacture the microemulsion defoamers, the presence of oil/alcohol is quite undesirable. The oil, in addition to causing environmental problems, has been known to cause spotting and surface tension problems with the pick-up rolls, and the short chain alcohols are either flammable or combustible causing the microemulsions to present a fire danger.
Thus an effective defoamer product for groundwood and thermomechanical pulping mills is needed which contains neither oil nor short chain alcohols. However, the industry has not been able to produce a stable emulsion product from the polyethylene glycol fatty acid esters in the absence of the oil and alcohol, which product has been an effective defoamer.
A defoamer that is generally cheaper than a microemulsion defoamer on a cost per pound basis plus does not contain oil or short chain alcohols is a water-based macroemulsion defoamer. These defoamers are widely used in screen rooms, paper machines, and effluent streams of Kraft mills. They generally contain 10 to 30% fatty alcohols (C12 to C24) and/or 1 to 10% saturated fatty acids (C12 to C24) and/or 1 to 3% long chain hydrocarbon (waxes) and 1 to 5% emulsifiers such as ethoxylated alcohols, fatty acids soaps, and ethoxylated fatty acid esters.
When Kraft mill macroemulsion defoamers are used in groundwood and thermomechanical pulp mills, they generally have been found not to work in adequately reducing foam and those few that have worked as defoamers have required such large quantities that they have not been sufficiently cost effective to be commercially acceptable.
Accordingly, the groundwood and thermomechanical pulp mills have long desired a water-based defoamer that does not contain oil and/or short chain alcohols and is cost effective in comparison with the currently used traditional defoamers. It is the object of the present invention to produce such a defoamer and to utilize it in groundwood and thermomechanical pulping mill operations.
The present invention is directed to a water-based defoamer composition which comprises a polyester polymer prepared by reacting (i) a dimer fatty acid and (ii) a fatty acid with (iii) a mixture of at least two polyalkylene polyols. The resulting polymer is readily water-dispersible and forms a macroemulsion in the absence of any oil and short chain alcohols. The polymer defoamer composition can be prepared by simply mixing about 10 to about 35% of the polymer into water.
Macroemulsions and microemulsions are readily distinguishable. A macroemulsion is generally opaque in view of the particles generally being about 400 or more microns in average diameter, whereas a microemulsion is generally transparent, in part because the particles are generally less than about 100 microns in average diameter.
A preferred dimer fatty acid suitable for this invention is a C36 aliphatic dibasic acid whose structure is essentially that of a long chain dicarboxylic acid with two alkyl side chains. It is derived from tall oil, animal, vegetable, or marine fats and oils, with the dimer fatty acid of tall oil being preferred.
Suitable dimer fatty acids are of the general formula: 
wherein R1 and R2 are each aliphatic groups containing about 8 to 12 carbon atoms, preferably 9; R3 and R4 are each alkyl side chains containing about 4 to 8 carbon atoms, preferably 6; X is selected from the group consisting of a single carbon-carbon bond, an ethylenic carbon-carbon double bond, or a monocyclic, acyclic, or bicyclic structure containing 4 to 8 carbon atoms, preferably 6; and at least one ethylenic bond. While the structure may be acyclic or bicyclic, the monocyclic structure is preferred.
The dimer fatty acid structure results from the dimerization of two unsaturated fatty acid molecules that form the dimer acid. The exact nature of the X linkage formed by the dimerization has not been completely defined. It may be as simple as a single carbon-to-carbon bond or as complex as a cyclic structure depending on factors such as the type of unsaturated fatty acid used and process conditions such as temperature and catalyst type. A suitable dimer fatty acid is available commercially as Empol(copyright) Dimer Acid from Henkel.
The fatty acid suitable for this invention is derived from tall oil, animal, vegetable, or marine fats and oils. Suitable fatty acids are of the general formula:
H3Cxe2x80x94(CH2)xxe2x80x94CHxe2x95x90xe2x95x90CHxe2x80x94(CH2)yxe2x80x94COOH
wherein x and y are integers such that the fatty acid contains a total of 8 to 22 carbon atoms, preferably 18. Alternatively, the fatty acid may be saturated or poly-unsaturated.
The dimer acid and fatty acid are reacted with compounds containing alcoholic hydroxyl groups to form the polyester. Co-monomers suitable to prepare the polymer are a mixture of at least two polyalkylene polyols having 2 to about 6 carbon atoms in the alkylene groups. Particularly suitable polyols are polyoxyethylene glycol of a molecular weight 200 to 1000, preferably 200 to 600; polyoxypropylene glycol of a molecular weight 400 to 4000, more preferably 1000 to 3000; polyoxypropylene triol of a molecular weight 400 to 4000, preferably 1000 to 3000; polypropylene-polyethylene glycol of a molecular weight 400 to 4000, preferably 1000 to 3000; and polyoxybutylene glycol of a molecular weight 400 to 4000, preferably 1000 to 3000.
The polyester polymer may be prepared in any suitable manner, but generally all the monomers including the fatty acid may be charged into a reaction kettle along with a conventional catalyst such as methanesulfonic acid, para-toluenesulfonic acid, hypophosphorous acid, or organotin derivatives. In addition, strong acids such as sulfuric and phosphoric acid may be used as the catalysts. With mixing and nitrogen sparge, the reactants are heated to about 300 to 400xc2x0 F. and held at that temperature until the acid value is sufficiently low. During the reaction water is removed, e.g. by means of a condenser and moisture trap.
The ratio of dimer fatty acid to fatty acid is generally about 1.1:1 to 10:1, preferably about 1.5:1 to about 3:1. The polyalkylene polyol polymers are generally used in a ratio of about 1:10 to about 10:1, preferably about 1:2 to about 2:1. The dimer fatty acid and fatty acid are used in slight molar excess to the polyols, e.g. about 5 to about 15%.
While the resulting 100% active polymer may be stored neat and then diluted extensively for use on site, preferably it is mixed into water to produce a water-based macroemulsion containing about 10 to 35% by weight polymer and about 90 to 65% water, and then it is this macroemulsion which is diluted immediately prior to use. To form the macroemulsion, the polymer, which may be end-terminated with either acid or hydroxy groups, is mixed into water with stirring, generally at about 80 to 100xc2x0 F. The stability and viscosity of the water-based macroemulsion defoamer may be controlled by the addition of additives such as thickening agents and the like. Suitable thickening agents include such as xanthan gum or polyacrylic acid neutralized by adding a suitable base such as sodium hydroxide, potassium hydroxide, ammonia, diethanolamine, or the like. Mixing for about 1 hour produces a stable, water-based defoamer macroemulsion with a viscosity in the range of about 200 to 1000 cp, preferably 300 to 600 cp, as determined by Brookfield Viscometer. There is no significant increase in viscosity and no separation for at least 3 months at room temperature, preferably at least 6 months.
Other potential additives include fatty alcohols (C10-24) and emulsifiable silicones. Generally these are used in small amounts, i.e. about 1 to 5% by weight based on the total weight of the macroemulsion. In addition, even smaller amounts, i.e. about 0.5 to 2% by weight, of a high melting wax may also be present.
The defoamer compositions of this inventions have particular utility in controlling foam and air entrainment in groundwood and thermomechanical pulping and paper making operations. Generally, the defoamer will find primary use in treating foams that could not previously be treated with water-based defoamers due to ineffectiveness and/or deposit build-up.
The diluted defoamer composition may be added to the system neat, or it may be further diluted with water, though generally there is no necessity to do so. Application points are best determined by on site inspection of foaming problems unique to that mill.
The quantity of the defoamer compositions required to control foam will obviously vary depending upon the specific nature of the foam to be treated and the individual components used to prepare the defoamers. Generally, however, a quantity of defoamer macroemulsion of from about 50 to 500 ml/min will be suitable, preferably 75 to 200 ml/min.